1. Field of the Invention
The present invention relates to a solid-state imaging device and an imaging apparatus, which are examples of a semiconductor device for detecting physical quantity distribution. More specifically, the invention relates to a mechanism including a plurality of arranged unit elements having sensitivity to electromagnetic waves input such as light or radiations from the outside, which reads out a physical quantity distribution converted into an electric signal by the unit elements as an analog electronic signal, converts the analog electronic signal into digital data, and outputs the digital data to the outside.
2. Description of Related Art
In recent years, as an example of solid-state imaging device, a Metal Oxide Semiconductor (MOS) imaging sensor and a Complementary Metal-Oxide Semiconductor (CMOS) imaging sensor have been attracted attention, which are able to solve various disadvantages of a Charge Coupled Device (CCD) imaging sensor.
For example, the CMOS imaging sensor has an amplification circuit for each pixel, such as a floating diffusion amplifier, and when the CMOS imaging sensor reads out pixel signals, as an example of address control, a method of a so-called column parallel output type or a column type is often used, in which one row in a pixel array unit is selected and pixels of the one row are concurrently accessed row by row, that is, all pixels of one row are read out from the pixel array unit, simultaneously and in parallel.
Further, the solid-state imaging device may adopt a method in which an analog pixel signal read out from a pixel array unit is converted into digital data by an Analog Digital Converter (A/D converter) and the digital data is output to the outside.
This is the same as the column parallel output-type imaging sensor, and various types of signal output circuits have been conceived. There has been proposed a method as one of the most advanced type, in which an A/D converter is provided for each column and a pixel signal is output to the outside as digital data (for, example, refer to Japanese Patent Application Publication No. 2005-278135).
Further, as an A/D conversion method, various methods have been considered in terms of the circuit scale, processing speed, and resolution. One of the A/D conversion methods is a so-called single-slope-integrating or ramp-signal-comparison A/D conversion method. In this method, an analog unit signal is compared with a reference signal used for digital signal conversion, and count processing is performed in parallel with this comparison operation. Based on a count value at the time of completing the comparison operation, a digital signal of a unit signal is obtained. This method is also adopted in the above-mentioned patent document.